Satellite navigation systems such as the Global Positioning System (GPS) can be used by receivers configured to receive satellite signal(s) to determine receiver location with a high degree of accuracy. Some receivers are equipped with supplemental sensors that provide inputs that are used in conjunction with satellite signals to improve the functionality of the receiver.
GPS availability has limitations that have become more noticeable as the range of GPS applications has increased. Many applications require uninterrupted (GPS) service regardless of whether the user is in an urban area, or in a mountain zone, under a tunnel, or in a bunker. Additionally, in recent years, jamming tactics affecting GPS devices are increasing, decreasing GPS availability and thus system accuracy even further.
In these cases, the GPS signal tends to either disappear completely or simply become intermittent, disrupting the navigation ability of the device. GPS signals may be supplemented with information from other sensor(s), such as inertial measurement units (IMUs), laser range-finders, or cameras, but also magnetic compasses, altimeters, speedometers, star trackers, and the like. This allows navigation to continue once the GPS-denied situation develops. However, the additional information from sensors only provides the required accuracy for a short period of time compared to when GPS is available. Further, additional sensors add to the size, weight, and power consumption of the device and are more costly to manufacture.